Prescriptive landfill legislation, guidelines and directives presently limit the hydraulic conductivity of compacted soil liners to 1×10−7 cm/s or lower. Presently sample testing liners can require between five and fourteen testing days when tested according to procedures specified by American Standard Test Method (ASTM) 5084-D. As a result of the long test times large sections of field compacted liners are not directly tested for hydraulic compliance. Present flexible wall bench testing techniques are time prohibitive and equipment intensive (samples must be transported to a laboratory for testing). Furthermore there is a lack of government and industry education.
A permeameter is used to determine the fluid transport properties of a porous medium. e.g. a compacted soil layer. A current method of testing employs a static bench permeameter with a hydraulic head applied via a pressure system. This type of testing requires a significant capital expenditure to implement, resulting in a significant per sample cost. Also the results are often untimely and are based on the questionable quantification of very small outflow volumes measured over short time periods. For impermeable samples (generally materials with a hydraulic conductivity less than 1×10−7 cm/s) augmentation steps may be employed to increase the amount of outflow volume over a shorter time period by applying a substantial fluid head to the sample either by a column of fluid or a pressurized system. This augmentation can result in the testing of samples with high fluid gradients and high fluid pressures within the sample.
Rigid wall centrifuge permeameters provide faster results and are potentially mobile. A problem that remains is how to seal the sample against the rigid sleeve so that fluid does not pass between the sample and the wall. Compacting the sample does not solve the problem—the sample is no longer in its natural state and the potential for leakage remains. However, the rigid wall construction of the permeameter may results in the testing liquid leaking past the sample along the rigid wall. This is particularly a concern.
It is an object of the present invention to provide a permeameter to obviate or mitigate at least some of the above presented disadvantages.